where \(P \in \lbrace X, Y, Z\rbrace \)  belongs to the set of Pauli matrices, and \(\theta \)  is the angle of rotation. The errors in the single-qubit gates stem from fluctuations in the laser beam's intensity and phase, which lead to over/under-rotations and changes in the axis of rotation, respectively [1]}. In the present work, we model these errors by a symmetric depolarising channel, which admits a decomposition in terms of Kraus operators [2]}, namely
\(\rho \rightarrow D(\rho )=\sum _nK_n\rho K_n^\dagger .\) 
